Oxidation process



Jan. 8,v 1946. c; DREYFUS 'l OXIDATION PROCESS Filed sept. 5, 1942(INVENTOR.

mm .mn b f b Imm SEIU Zorro/um .mufcmnm s mv Emmen? m mm om K mm NmkCamille DrjeHf-us BY\ 9 ATfroRNEY'Sv Patented Jan. 8, 1946 UNITEDSTATES PATENT OFFICE oxmnrrofn mtoenss Camille Dreyfus, New York, N. Y.Application September 5, 1942, Serial No. 457,381 1 Clam. (ci. lzoo-533) This invention 'relates tothe oxidation 'of hydrocarbons andrelates more particularly 'to the Aoxidation of unsaturatedhydrocarbons. 1

An lobject of rnyinyention is to oxidize unsaturated hydrocarbons toproduce valuable oxygen- 1 trial heating media `since the gaseouscombustion f vreaction may 'be leasily and accurately controlled. Whilethe gas mixtures are valuable las heating media, they Aareeven morevaluable as a raw material for the manufacture of -various oxygenu,

1ated organic compounds.

I have now discovered lthat unsaturated aliphatic `gaseous hydrocarbonsmay be oxidized at' elevated temperatures zand pressures Zwith Treeoxygen to yield valuable foxygenatedorganic compounds. "The productswhich may 'be obtained in Vaccordance ywith vmy invention are, "forexample, ethylene oxide, acetaldehyde, ethyl falcohol, acetic acid,formaldehyde, methyl 'alcohol, acetone and Ahigher =ketones andalcohols.

`The gaseous mixtures containing Aunsaturated aliphatic gaseoushydrocarbons vremployed in accordance with `my -no'vel process may bobtained from any suitable source. Preferably, the `gaseous mixturesemployed are those obtainable 5by cracking saturated lhydrocarbons and1mixtures of said hydrocarbons, Jeither 1in the liquid or vapor phase,which produces a mixture oi gases vpredominantly unsaturated incharacter, containing substantial quantities of ethylene vand higheriunsaturated aliphatic hydrocarbons. 'The charging Astock supplied tothe cracking unit lmaybe either liquid or gaseous infcharacter. 'Theconditions of 4operation-in rthe cracking unit may be vared'to handlethe diierent Itypes of charging Ystock and to crack them vto maximumyields of unsaturated aliphatic hydrocarbon gases. :The cracking unitmay operate at temperatures fof from 1000 to 2000'-F. and thepressuremayrange ,from subatmospheric pressures of from yabout d. vpound per'square inch wabsolute to "super-atmos- -pheric pressures of 15 to 200pounds per square inch absolute.

vIn carrying out the oxidation of the gaseous unsaturated aliphatichydrocarbons, ;Eree oxygen may be employed. y Preferably, I employ airas the source of oxygen Ialthough any mixture com prisi-ng oxygen and.suitable inert diluents vxis suitable. The oxidation reaction may be4carried out at temperatures of from 400v to 800 F. while the pressureemployed maybe fromslightly above atmospheric pressure to pressures of`500 pounds per square 'inc-h gauge.

For the oxidation reaction, the ratio Iof roxy,- lgen employed -to the`volume yof gaseous unsaturated hydrocarbon employed, Jmay wary. .Satis-Afacto-ry results Amay be' Aobtained if, for each wolume of lgaseoushydrocarbon added -to thesys tem, there are added from 3 to ll0-Vrvolumes of air While lat the `same time from 20 'to 80 Volumesofunreacted hydrocarbon gas are recycled. Op-y timum results are obtainedWhenthere are added to the -systemabout 7 volumes of air lfor each -vol`urne of gaseous 'hydrocarbon and 50 "volumes of lgaseous hydrocarbonsare recycled.

After the oxidation reaction the oxygenated products, together with the11n-reacted gases, are passed -to an absorption system wherein theoxygenated products are separated. The absorption #system also -mayvoperate under pressure. =The unreacted hydrocarbon gases are removed4lrom the ga-ses 'which remain and are recycled to the 'oxidation zone.-The nitrogen, carbon monoxide, carbon dioxide and oxygen `which remain:after reiriovalfof the hydrocarbon gases are then-#vented 'to theatmosphere.

AThe Aprocess -of my invention will V-now lbe-described with're'ferenceto the accompanyingfdrawing.

`The vcharge stock, which is cracked to yield the gaseous `-mixture `ofunsaturated aliphatic hydrocarbons, is caused to `enter Lthe systemthrough a line l. The Lstock fis forced in under the desired pressurebya pump! 2 `which --may be -either -a liquid pump or a gas compressor,vde'penizling upon `Whether or |not the charging rstock is liciu'id 'vorgaseous 4'in nature. When l'the cracking unit is loperated undersub-atmospheric pressures, `the pump xmay-be 4eliminated for ibyepassed.4From pump'2, the chargingstocklis passed through :a line s3 totheVcracking furnace 4 -where it lenters coils t'5 and-6 and is #heated itocracking temperature. The vcracking temperature zwill :vary der pending-upon the naturefof the scharging stock.

From 'the lfurnace, the v`cracked mixture r-itlows throughaline -1 to afractionating ftower matter having been quenched by a portion of theresid` ual product from the bottom of the fractionating tower 8. Thequenching liquid is drawn through a line 9 and forcedby a pump Illthrough a cooler II and into line 1. This quenching operation serves toarrest the cracking reaction and to reduce the temperature at the baseof the fracl Y. tionati-ng tower. Heavier residual liquid productsformed Vin the cracking operation are removed from the baseof thetowerthrough line I2v which is providedwith 'a valve I3. The cracked gaseousmixture passes' overhead from the tower through line I4, enters acondenser I5 and is collected in a receiver I6. A portion 'of thisgaseous mixture condenses and accumulates at the base of rel, ceiver I6.This liquid Vis returned to the top of the fractionating tower as a reuxmediumv through pump I1 and line lI8. Any excessliquid j condensationproduct accumulating in the ,re` ceiver I6 may be removed from thesystemy V.through line I9 which isprovided with avalve 20.

This excess liquid may be returned to vthe charg-` ing .stock andYrecycled through r the process to AHThe cracking unit may operate undersub-atmospheric or super-atmospheric pressures. Whengoperating undervsuper-atmospheric pres- 'surethe pressure'r is controlled by valve 2|with Vvalve 22 closed and valve A23 open. When opering zone lfor furthervcracking by meansof a compressorj21l through lines 2,84 and V429 inorder to increasethe proportion of unsaturated hydro-v carbonsin thegases.V Y

' 'Phe-gaseous mixture ofk unsaturated aliphatic hydrocarbonsfrom holderl26 is charged tothe oxidizing section through line30 by means of adizingwzone On the upstream side ofthe prescompressor 3I whichcompresses the gas frornithe gas holder pressure'to therhigher operatingp ressure required4 inthe oxidizing section. The charge ofgasis joinedbyv recycle gas which enters through a line 32. Air is forced into themixed gases inline by a compressor 33, the air entering through a line34. The mixture of charge gas, cycle gas, and airV is then passed to4the furnaceg35. where itenters coils 36 and is brought lupto optimumreaction temperature. The oxidizing reaction is continued inthereactionchamber 31 located just beyond the furnace discharge. rTheYreaction chamber 31 is so designed as to provide a variable' volume andin this wayY the reaction time may be controlled.V The smaller theYvolume provided, the Yshorter will be the Areaction period since, with agiven volumetric velocity, the reacting gases will pass through y thereaction chamber after being subj'ectedto the reaction conditions foronly a relatively short period-,of time. ,The greater the volumeprovided, with the same volumetric velocity, the longer will be lthereaction time, due to the more extended period during which the4reacting gases are subjected tov reaction conditions. As the hoil gasmixture leaves the. reaction,r chamber, it is quenched .bythe injection.of cold liquid at 3 8 Y throughjline .39v andthe whole mixture Viscooled in a cooler 40 andy ows through a line 4I to a separator42. Aportion of ithellquid condensate Vis returned through al line 43by-a'pump 44 to enter at 38 and to quench the hot gases leaving thereaction chamber 31. Y

The reaction chamber of variable volume may comprise a reactorcontaining a movable piston which is adjustable so that the volume ofthe reaction chamber may be increasedor decreased.

A variable effective volume may also be obtained f of Vthe reactionchamber may be. varied. If, for example, the discharge port furthestfrom the inlet is opened and the others closed, the reactclosest to theinlet is opened and the remainder closedrthe reacting gases will be inthe reaction chamber foronly a relatively limited period and thereaction .time will be quiteshort. n'

The liquefied portion of the products in separator Y42 is withdrawnlthrough a line 45 provided with a valve 46 and directed to a recoverystage (not shown). This product contains formaldehyde and a small'amount Vof recoverable volatile products in water solution. Thevolatile products are removed fromV this solution and the formaldehydemay be concentrated to a suitable concentration of commercial utility.

The gaseous portion of the oxidized products leavesseparator 42 throughline 41 yand enters an absorber 48 whereV the water-soluble componentsare absorbed in waterrentering the top of the absorber through line 49.4'The absorber is operated under a pressure of, for example, pounds persquare inch. This pressure vis controlled by the pressure control *valveV50.. lI'fhis valve-likewise controls the pressure on theoxisurercontrol valve 50, a portion of the gas which is unabsorbed isrecycled through line 5I, booster the Water-soluble products dissolvedtherein, is

removedfrom the base of the'rabsorberthroilgh line 53v and valve 54 andis passed' through a heat interchanger 55 and then through a line 56`into a recovery still 51 for recovery of the volatile products.Stillv51 operates atsubstantially atmospheric pressure.` i The volatile,water-soluble ,products are distilled overheadY through a line 58 and acondenser 59'ar1d collected in the receiver 60. A portion of thevcondensate iromvrthe receiver 60 is returned to the top of the towerfor reiiux medium throuh pump 6I and line 62.` Still .51 maybe heated.by any conventional means such as by a steam heating coil. I3.`y Aportion of the stripped aqueousresiduefrom the base'of the still isreturned byline 64 andr pump.l 65 through heat exchanger 55 and cooler66.1t`o'the absorber 48'to be used for absorbing more watersolublevproducts. VExcessstripped watery is removed from the still through line-61 which is provided with a valve 68. The condensed Ap'rodf uctcollected in receiver L6I) is a mixtureof ,ethf ylene oxide,acetaldehyde, ethyl alcohol,Y acetic acid, methyl alcohol,iacetone,andhigher alcohols and Aketones, and this mixture is'directed through aline69ftora purication' stage (not shown), where the mixturelmaybelseparated intofuseveral individual components in 'anysitablemanner. Y:f as

through pressure control valve 50 contains unconverted hydrocarbongases, together with nitrogen, carbon monoxide, carbon dioxide and asmall amount of oxygen remaining from the air injected into the system.This gas passes through a line 1D to a gas absorption unit. This unitcomprises an absorber 1| and a still 12. The entering gas flows upwardand counter-current to the downward flow of absorber oil which entersthe top of the absorber through line 13. The desired pressure ismaintained on the absorber 1| by a pressure control Valve 14 and is heldat a point somewhat below the operating pressure in the absorber 48 inorder to permit ow of the gas through line to absorber 1|. The downwardflowing absorber oil absorbs the hydrocarbon gases. The remaining gas,free of hydrocarbon constituents,l leaves absorber 1| through a ventpipe 15 and is discharged to the atmosphere.

The absorber oil containing the absorbedhydrocarbon gases is dischargedfrom the base of the absorber 1| through line 16 and is forced by a pump|1 through lheat exchanger 18, a preheater 19 and a line 80 intorecovery still 12. In this still the dissolved hydrocarbon gases aredistilled overhead through linev 8| and enter a condenser 82 where theyare cooled and partially liquefied. The partially liquefied productenters a receiver 83 for collection and separation. The temperature ofcondenser 82 is adjusted so that only that amount of liquid required forreiiux in still 12 is condensed. This liqueed portion is returned asreux to the top of still 12 by a pump 84 through line 85. The balance ofthe recovered hydrocarbons are discharged as a gaseous mixture throughpressure controller 86 and are recirculated to the furnace 35 throughline 81. The pressure on still 12 is maintained at a point high enoughto return the hydrocarbon gas mixture from receiver 83 back to theoxidizing furnace under its own pressure.

Recovery still 12 may be heated by any convenient means such as a steamcoil 88. 'I'he stripped absorption oil is then returned to the top ofthe absorption tower by a pump 89 through lines 90 and 9|. The oilpasses through heat exchanger 18 and a cooler 92 and enters the top ofabsorber 1| through line 13. Fresh absorber oil may be supplied to thesystem through a line 93.

The operation of my novel process is relatively simple and producesexcellent yields of oxygenated products without the formation ofexcessive amounts of tar and other products such as carbon monoxide andcarbon dioxide.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis:

Process for the production of oxygenated organic compounds, whichcomprises mixing one volume of a gaseous unsaturated aliphatichydrocarbon with about 7 volumes of air and adding to said mixture aboutvolumes of anhydrous unreacted gaseous unsaturated aliphatic hydrocarbonrecycle, heating the anhydrous mixture to a temperature of 400 to 800 F.while under a superatmospheric pressure of not more than 5'00 pounds persquare inch, passing said reacting mixture to a Vcatalyst-free reactionzone, allowing. the reaction to continue therein to form oxygenatedorganic compounds, condensing the mixture of gases formed and injectinga portion of the condensate into the gaseous mixture leaving thereaction zone to halt further oxygenation.

CAMILLE DREYFUS,

Nef

